The U.S. Pat. No. of Cuneo et al. 5,085,161, issued Feb. 4, 1992, discloses a method and an apparatus for fabricating from steel plate subassemblies which are joined to one another and to transverse bulkheads to provide modules which are then serially joined to provide a longitudinal midbody for a double-walled tanker hull. Bow and stern sections are added to complete the hull. According to the method disclosed in this prior patent, much of the fabrication of the subassemblies is conducted using a set of towers which hold and position the various curved plates of the inner and outer hulls, and the wall-connecting plates, all arranged on end, as electrogas or electroslag welders vertically create T-joints among the respective sets of three juxtaposed plate edges.
The U.S. Pat. No. of Goldbach et al. 5,090,351, issued Feb. 25, 1992, discloses certain improvements, e.g., for bending the curved plates, and welding, cleaning, painting and assembling the various elements of the modules and for serially joining the modules to provide the longitudinal midbodies.
The U.S. Pat. No. of Goldbach et al. 5,086,723, issued Feb. 11, 1992, discloses an elaborated double-hulled vessel, in which each midbody module further includes a double-walled longitudinal bulkhead which can be fabricated as a subassembly using the methods and apparatus disclosed in the aforementioned U.S. Pat. Nos. of Cuneo et al. 5,085,161 and Goldbach et al. 5,090,351. An improved form of the longitudinal bulkhead (and other subassemblies of the double-walled vessel hull), which provides longitudinally staggered cell-to-cell access openings through the longitudinal wall layer-connecting plates is disclosed in the U.S. patent application No. of Goldbach 07/953,141, filed Sep. 29, 1992.
According to a further development that is disclosed in the copending U.S. patent application No. of Goldbach et al. 07/818,588, filed Jan. 2, 1992, the newly fabricated modules are turned from their initially upended orientation to an upright orientation using a two-section floating drydock. One section is equipped with the module-rotating device. The two drydock sections can be independently flooded and pumped out for acquiring modules and shifting the growing midbody so as to spatially position the site where two modules are to be joined so that it is effectively between the two sections. Therefore, the drydock sections can be adjusted in several degrees of freedom relative to one another for correctly matching the module ends which are to be welded. Also in this prior document, there is disclosed the concept of building the midbody in two multiple-module portions, one having the bow section joined at one end, and the other having the stern section joined at the opposite end. These two complementary vessel hull portions are then joined to complete the hull.
For use in instances where a flat hull surface is desired, such as for the inner wall of the bottom of a cargo vessel hull, the concepts embodied in the abovementioned earlier patent documents can be modified to provide all or a portion of either wall layer of the double-walled vessel hull to be made of flat rather than curved plates, as disclosed in the U.S. patent application No. of Goldbach 08/033,357, filed Mar. 18, 1993.
Having now given more thought to the overall process and to the apparatus used for fabricating the plates, subassemblies, modules, midbodies and vessel hulls, the present inventors have devised some improvements particularly for practicing an intermediate part of the process. For those following the process as described in the aforementioned U.S. Pat. No. of Goldbach et al. 5,090,351, the improvements provided by the present invention come into play at a stage after the curved and stiffened flat panels have been fabricated and painted, preferably using the cathodic epoxy coating system which is described at that patent. After the modules are fabricated from those panels using the improved process and apparatus of the invention, the modules can be serially joined using the methods and apparatus disclosed in any of Cuneo et al. U.S. Pat. No. 5,085,161, Goldbach et al. U.S. Pat. No. 5,090,351 and Goldbach et al. U.S. Pat. No. 07/818,588.